Abstract <p>Over the past few years, assessment of water pollution has been carried out in dam ponds, flooded quarries, and diggings located in the Cis-Ural region (Udmurt Republic). This is a significant environmental and hygienic problem for the region due to the diversity of sources supplying pollutants to drainage landscapes and water bodies. It was found that the increase in water mineralization in the reservoirs studied is primarily influenced by the technogenic load on their catchments, which is associated with the impact of oil production or urbanization. The process of secondary technogenic salinization of such reservoirs is accompanied by a statistically significant increase in the number of species in the fish communities, mainly due to the appearance of some short-cycle and low-value representatives of ichthyofauna. The obtained data on the reactions of aquatic organisms using the example of the actual composition of the fish population can be used as biological indicators of the quality of water resources in man-made reservoirs. In hygienic and environmental assessments, they can be used as criteria in addition to the chemical indicators of the state of waters and the natural resource and economic potential of the corresponding water, coastal, and drainage landscapes.</p>